Extended depth of focus, range extraction [1] and super resolved imaging [2-3] of imaging systems are three very important technologies investigated in the fields of imaging. Extending the depth of focus allows imaging system incorporation into various applications, including inter alia medically related applications where elements, such as cameras, are to be inserted into the body in order to observe and detect problematic tissues; as well as ophthalmic industry including glasses for spectacles, contact lenses, intraocular lenses or other lenses inserted surgically into the eye. The extended depth of focus solution is also needed for optical devices like microscopes or cameras for industrial, medical, surveillance or consumer applications, where focusing of light is required and where the conventional focusing techniques is based on the use of a multitude of lenses with the need of relative displacement between the focusing arrangement and an imager and/or object plane, by mechanical movement, either manually or electronically driven. A lot of approaches have been developed dealing with extended depth of focus based upon aperture coding, some of which are all-optical as described in Reference [4] and also in the US patent publication US2006/034003 assigned to the assignee of the present application, and some required digital post processing [5-9] in order to extract the focused image.
Many techniques were developed to deal with range extraction mainly by extraction of shape from shading while computing the gradients obtained in the image [10-12], scanning the object with a line and observing its curvature [13-14], high speed scanning based on active laser triangulation and a variety of fast to even real-time scanners [15] and triangulation [16-17].
Super resolution is an explored topic as well [2-3]. The resolution of a lens-based imaging system is defined by the finite dimensions of a lens. The resolving power or the minimum separation between two points which can be resolved is limited by the diffraction that takes place in the imaging system (e.g. microscope) because of the wave nature of light. Techniques aimed at achieving the super resolution deal with extending the resolution limit set by diffraction caused by the physical dimensions of the optics. The term “super resolution” refers to spatial resolution which exceeds the diffraction limitation caused by the wave nature of light, and signifies a resolution which is greater than one-half the wavelength of the light actually being used. Digital imaging provides for exceeding the limit set by a non-zero pixel size of a photodetector (e.g., CCD), i.e., the geometrical resolution. The geometrical super resolution may also be based upon orthogonal aperture coding as described in WO2004/102958 assigned to the assignee of the present application and references [18; 19].